Vent system for a cooking appliance

ABSTRACT

A vent system for a cooking appliance is disclosed. The appliance has a cooktop surface supporting a plurality of surface heating units. The vent system includes a vent box mounted beneath the cooktop surface; a telescopic vent assembly telescopically mounted relative to the vent box, the telescopic vent assembly being movable between a retracted position proximate the cooktop surface and an extended position above the cooktop surface; a retention unit configured to releasably hold the telescopic vent assembly in the retracted position; and a stored energy mechanical drive unit configured to move the telescopic vent assembly in a first direction to the extended position upon release of the retention unit.

BACKGROUND OF THE INVENTION

The exemplary embodiments of the invention relate generally to vent systems. More particularly, the exemplary embodiments relate to downdraft vent systems for a cooking appliance.

Some downdraft cooktops have a four-burner layout where there are two burners on either side of the downdraft vent. Generally, for gas cooktops, the downdraft vent is located in the middle of the burners with its vent inlet being substantially flush with the top surface of the grates. The grates rest on the cooktop surface directly above the gas burners. On electric cooktops, there are no grates and the vent inlet is basically flush with the cooking surface. When the downdraft vent is activated, part of heat from under and around the bottom of a cooking utensil placed on the cooktop is pulled directly into the downdraft vent before it has a chance to heat up the utensil and its contents since this path represents the path of least resistance into the vent. In addition, when the cooktop includes gas burners the burner flames as well as the heat is drawn or pulled toward the downdraft vent. Allowing the burner flames to be drawn into the downdraft vent affects the performance of the burners, which generally makes the available or effective burner sizes smaller. As a result of the heat loss and lower burner ratings (i.e. smaller burner sizes) the ability of the downdraft cooktop to, for example, boil water or other fluids is negatively affected. For example, it can take a downdraft cooktop almost an hour to boil a six-liter load compared to the fourteen or fifteen minutes it takes a non-downdraft cooktop to boil the same load.

Moreover, generally a downdraft vent with its vent inlet being substantially flush with the top surface of the grates on gas cooktop appliances and flush with cooktop surface on electric appliances is also positioned such that it cannot optimally capture steam and smoke coming out of the utensils during cooktop use. To overcome this deficiency, the fan, which is located under the cooktop appliance and downstream of the vent inlet, will generally be sized for large airflow movement to obtain the desired smoke and steam capture rates. These large rates come at the expense of higher noise emissions, larger room energy losses from ambient room conditions, and even lower efficiencies in delivering heat from the burners to the cooking utensils.

Other downdraft cooktops have separate telescoping vent hoods that generally attach behind the cooktops. U.S. Pat. No. 3,409,005 discloses a backside retractable ventilating flue. Others have made refinements to this approach, but these telescoping vent hoods take up additional space, making the cooktop larger and are located remotely from the cooking zones thereby decreasing their venting effectiveness. When the cooktop appliances are installed in kitchen island located in the middle of the room, the separated telescoping hoods are not practical from both esthetic and practical standpoints as they interfering in an unsafe manner with accessing utensils from the back side of the appliances.

Still other downdraft cooktops have a rotatable vent hood. In a retracted position the vent hood may be flush with the cooktop surface. In its extended position the vent hood is rotated about a fulcrum so that the vent hood is above the cooktop surface. However, the height of the vent hood is relatively limited. Moreover, this vent arrangement prevents the use of the middle section of the cooktop for moving and resting utensils.

There are other variations where telescoping vents have been incorporated as an integral part of the downdraft cooktops. These approaches require either manual adjustment to properly position vent into extended position or use of a motor to extend vent hood into place. Manual adjustment requires a certain level of dexterity, additional time to set up and potential exposure to hot components when the vent is not extended prior to using the cooktop. Motorized approaches address the setup time and hot component exposure issues, but they are prone to being activated when cooking utensils may be in the path of the extended vent. This can lead to unsafe conditions to the consumer and damage to the household. In addition, motorized approaches require additional complexity in its control to avoid overloading the motor or damaging the vent components, which generally adds to lower overall reliability of the cooking appliance.

This invention proposes a simplified, non-electronic approach to extend the telescoping vent, while maintaining the natural advantages of more efficient cooktop operation and better smoke/steam capture. In lieu of manual or motorized approaches to extend the vent, a stored energy mechanical drive unit is used to smoothly extend the vent to its fully extended position.

BRIEF DESCRIPTION OF THE INVENTION

As described herein, the exemplary embodiments overcome one or more of the above or other disadvantages known in the art.

One aspect of the exemplary embodiments relates to a vent system for a cooking appliance of the type having a cooktop surface supporting a plurality of surface heating units. The vent system includes a vent box mounted substantially beneath the cooktop surface; a telescopic vent assembly telescopically mounted relative to the vent box, the telescopic vent assembly being movable between a retracted position proximate the cooktop surface and an extended position above the cooktop surface; a retention unit configured to releasably hold the telescopic vent assembly in the retracted position; and a stored energy mechanical drive unit configured to move the telescopic vent assembly in a first direction to the extended position upon release of the retention unit.

Another aspect of the exemplary embodiments relates to a cooking appliance. The cooking appliance includes a cooktop surface; a plurality of surface heating units located on the cooktop surface; and a vent system. The vent system includes a vent box; a telescopic vent assembly telescopically supported by the vent box, the telescopic vent assembly being movable between a retracted position where the telescopic vent assembly is substantially disposed within the vent box and an extended position where part of the telescopic vent assembly is disposed above the cooktop surface; a retention unit configured to releasably hold the telescopic vent assembly in the retracted position; and a stored energy mechanical drive unit configured to move the telescopic vent assembly in a first direction to the extended position upon release of the retention unit.

These and other aspects and advantages of the exemplary embodiments will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. Moreover, the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic, top view of an exemplary cooking appliance incorporating a vent system in accordance with an exemplary embodiment of the invention;

FIG. 2 is a schematic, partial, perspective view of a vent system in accordance with an exemplary embodiment of the invention;

FIGS. 2A and 2B are partially, schematic illustrations of the vent system of FIG. 2 in retracted and extended configurations; FIG. 2C schematically illustrates how a linear spring and a rotary damper engage the vent duct of another embodiment of the vent system; FIG. 2D is an enlarged, perspective view of the rotary damper of FIG. 2C;

FIGS. 3A and 3B are schematic, partial, perspective views of a vent system in accordance with an exemplary embodiment of the invention in retracted and extended configurations, respectively;

FIGS. 4A and 4B are respectively schematic perspective and side views of a vent system in accordance with an exemplary embodiment of the invention in an extended configurations;

FIG. 5 illustrates an exemplary intake airflow pattern for a vent system of FIG. 4A;

FIG. 6 is a graph illustrating an amount of air pulled from a bottom region of a cooking area relative to a distance of a vent inlet of the vent system of FIG. 4A above a cooktop surface; and

FIG. 7 is a graph illustrating an amount of airflow from a bottom region of a cooking area and a top region of the cooking area relative to a distance of the vent inlet of the vent system of FIG. 4A above the cooktop surface and relative to boiling time.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION

FIG. 1 illustrates an exemplary cooking appliance 100 incorporating a vent system in accordance with an exemplary embodiment of the invention. By way of example only, the cooking appliance 100 is shown as a cooktop 100 installed on countertop 190. However, the exemplary embodiments described herein may be used in other types of cooking appliances including, but not limited to, free standing ranges, slide in ranges and drop in ranges. It should also be understood that the exemplary embodiments may be used in cooking appliances with any suitable burner/heater types, including but not limited to, electric, gas and induction burners or any combination thereof.

As can be seen in FIG. 1, the cooktop 100 includes a cooktop surface 101 having a generally rectangular shape, although in alternate embodiments the cooktop surface 101 may have any suitable shape. In this example, four surface heating units 110A-110D are arranged in a two by two array (e.g., two rows and two columns) on the cooktop surface 101. The surface heating units 110A-110D may be electric surface units, gas burners or induction units. The cooktop 100 also includes surface unit controls 120A-120D, which are shown as being located to a side of the cooktop surface 101. A telescopic vent system 130 is located in this example toward the back 101B of the cooktop surface 101, although in alternate embodiments the vent system 130 may be located to the sides or front of the cooktop surface 101. It is noted that the configuration of the cooktop 100 shown in FIG. 1 is for exemplary purposes only and in alternate embodiments the cooktop 100 may have any suitable configuration and any number of surface heating units, controls and vents suitably positioned relative to the cooktop surface 101. For example, the cooktop 100 may include more than two rows of surface heating units where a telescopic vent is positioned between each or every other row of surface heating units. In another example, the surface unit controls may be located along the front 101F of the cooktop surface 101 or on the countertop 190 or corresponding cabinet adjacent the cooktop 100.

Referring to FIG. 2, an exemplary embodiment of the telescopic vent system 230 is shown in an extended configuration. As can be seen in FIG. 2, the telescopic vent system 230 is supported by the cooktop surface 101 (the surface heating units are not shown in FIG. 2 for clarity). In this example, the telescopic vent system 230 includes a vent box 240 and a telescoping mechanism 290 movingly mounted at least partly within the vent box 240. The vent box 240 may suitably mounted to, for example, the underside of cooktop surface 101 and be in flow or fluid communication with a fan 102 through suitable duct work for pulling in, for example, steam, smoke and other airborne particles from the cooking area and routing the exhaust gas to a suitable outlet. In one example the outlet may include filter(s) for removing particles and odors from the exhaust gas. In one exemplary embodiment, the fan may be configured to draw a flow rate of about 500 CFM (Cubic Feet per Minute) through the vent system 230. In alternate embodiments the flow rate of air flowing through the vent system 230 may be more or less than 500 CFM.

The telescoping mechanism 290 includes a telescoping vent duct 234 and a duct cover or lid 236 located at the upper end of the vent duct 234. In this example the vent duct 234 and the duct cover 236 are shown as having a substantially rectangular cross section, but in alternate embodiments the vent duct 234 and the duct cover 236 may have any suitable cross section including, but not limited to, round, trapezoidal, triangular and octagonal. A vent inlet 235 may be located through the duct cover 236 and/or on at least one side of the vent duct 234 so that the vent inlet 235 is in flow or fluid communication with a fluid passage of the vent duct 234. In this example the vent inlet 235 is shown as a rectangular slot for exemplary purposes only. In other exemplary embodiments the vent inlet 235 may have any suitable shape and size. The vent inlet 235 may also include a grille or grate to, for example, keep relatively large foreign objects from entering the vent duct 234. The vent inlet 235 may be configured to muffle the sound of the airflow and/or fan noise for reduced noise generation during the operation of the vent system 230. The vent duct 234, the vent cover 236 and the vent inlet 235 will be referred to herein for exemplary purposes as the telescopic vent assembly 233. The vent assembly 233 may protrude through a mounting plate or grate 280 located on (or recessed in) the cooktop surface 101 so that in a retracted position the duct cover 236 is recessed within the mounting plate 280 and the vent inlet 235 is sealed against a surface of the mounting plate 280. For example, as can be seen in FIG. 2 the mounting plate 280 may include a tapered recess 281. The vent cover 236 may have a substantially flat top with sides that are tapered so that the sides fit within the tapered recess 281 where, when the vent assembly 233 is in a closed or retracted configuration (see e.g. FIG. 2A) the top of the vent cover 236 is substantially flush with the top surface 280S of the mounting plate 280. In alternate embodiments, the top of the vent cover 236 may have any suitable shape (e.g. rounded, ribbed, etc.). The vent inlet 235 may be located on the side of the duct 234 (or of the vent cover 236) such that when in the retracted configuration the tapered recess 281 effectively closes off and substantially seals the vent inlet 235. In alternate embodiments the mounting plate recess 281 and the vent cover 236 may respectively have any suitable reciprocal shapes so that the vent inlet 235 is closed. It is noted that while the top surface 280S of the mounting plate 280 is shown located above the cooktop surface 101, in alternate embodiments the top surface 280S of the mounting plate 280 (and the top of the cover 236) may be substantially flush with the cooktop surface 101. The duct assembly 233 may also include a filter 231 located within the vent duct 234, adjacent to and preferably downstream of the vent inlet 235, for example, to capture and prevent grease and/or other particles from entering the vent ductwork and depositing on or damaging the fan 102. The filter 231 may be located such that it is easily removable for replacement and/or cleaning.

The vent system 230 may also include a mechanical drive unit 270 for causing the duct assembly 233 to move in the direction of arrow 299 to the extended position shown in FIG. 2B. The mechanical drive unit 270 may be any suitable drive unit that does not require a motor for movement. However, in alternate embodiments a motor and suitable power transmissions may be used to drive the vent assembly 233 between the extended and retracted positions.

In one exemplary embodiment the mechanical drive unit 270 may include a stored energy system such as a spring system that provides a steady and/or gradual movement of the duct assembly 233 in the direction of arrow 299, but preferably with a feed control mechanism such as a rotary damper, an air snubber or a hydraulic dampening piston. For example, the spring system may include a spring, one end of which is attached to the vent box 240 and the other end of which is attached to the vent duct 234. In the retracted position, the spring is extended. As a result, when the vent assembly 233 is free to move, the spring contracts, thereby moving the vent assembly 233 to its extended position.

FIG. 2C shows another embodiment of the spring system wherein a linear spring 270A is used. One end of the linear spring 270A is attached to the vent duct 234 at point D, the other end is attached to a rod 271 attached to a guide sleeve 240A of the vent box 240. Preferably, the mechanical drive unit 270 also includes a feed control mechanism which is used to control the moving speed of the vent duct 234 when it extends outward. In the embodiment of FIG. 2C, the feed control mechanism includes a rotary damper 270B attached to the guide sleeve 240A, and an elongate slot 234A formed on the vent duct 234 for receiving the rotary damper 270B. As shown in FIG. 2D, the rotary damper 270B includes a main body 272 and a gear 273 which is rotatably attached to the main body 272 and engages matching teeth formed on one lateral side of the slot 234A. The rotary damper 270B is configured to provide a damping only when the vent duct 234 moves outward. One of the functions of the rotary damper 270B is to ensure that the vent assembly 233 is not extended at an accelerating speed. The rotary damper 270B is known in the art, and therefore will not be discussed in detail here.

In one example, the linear spring 270A and/or the rotary damper 270B may be configured to fully extend the vent assembly 233 from the retracted position to a predetermined distance B (see FIGS. 4A and 4B) within a period of about one to about three seconds. In alternate embodiments the linear spring 270A and/or the rotary damper 270B may be configured to fully extend the vent assembly 233 in less than about one second or more than about three seconds.

In alternate embodiments the mechanical drive unit may include magnets, compressed fluid or any other suitable device configured to store energy for moving the vent assembly 233.

As clearly shown in FIG. 2B, a seal 282 may be provided between the mounting plate 280 and the vent duct 234 to at least partially control the rate of extension of the vent assembly 233 relative to the vent box 240 by friction as well as to provide a seal for preventing foreign objects such as cooking debris from being drawn into the vent box 240 through gaps that may exist between the vent duct 234 and the mounting plate 280. In alternate embodiments dampers of the mechanical drive unit 270 may, by themselves, control the rate of extension of the vent assembly 233. In still other alternate embodiments, the seal 282 alone may control the rate of extension of the vent assembly 233, by for example, frictional engagement with the vent duct 234. In yet other alternate embodiments the rate of extension of the vent assembly 233 may be controlled in any suitable manner.

As can be seen in FIGS. 2A and 2B, the vent system 230 may include a detection unit including one or more relay switches 260, 261 to detect when the vent assembly 233 is in the extended or retracted positions. In this example, two relay switches 260, 261 are shown in the vent box 240 where one switch 260 is located at the top of the stroke of the vent assembly 233 and the other switch 261 is located at the bottom of the stroke of the vent assembly 233. The vent duct 234 may include relay triggers including, but not limited to, protrusions, recesses and/or field generating devices (e.g. magnetic or otherwise). The relay switches 260, 261 may be configured to sense the relay triggers for detecting a position of the vent assembly 233. In other embodiments one relay switch may be configured to detect both the extended and retracted positions of the vent assembly 233. In one exemplary embodiment, the relay switches 260, 261 may be configured such that the vent system 230 may only be operated for venting when the vent assembly 233 is in the fully extended position as shown in, for example, FIGS. 2 and 2B. In alternate embodiments the vent system 230 may be configured to draw in air even during extension of the vent assembly 233 to its raised or extended position.

The vent system 230 may also include a retention unit for holding the vent assembly 233 in the retracted position. As can be seen in FIGS. 2A and 2B, the retention unit includes one or more latching members configured to hold the vent assembly 233 in the retracted position. In one exemplary embodiment the mechanical drive unit 270 may be configured to hold the vent assembly 233 in the extended position (by for example, the linear spring 270A shown in FIG. 2C) and the retention unit may be configured to hold the vent assembly 233 in the retracted position. In alternate embodiments there may be more than one latching members (e.g. latches 263, 262) which are configured to releasably hold the vent assembly 233 in the retracted and the extended positions, respectively. The latching members 262, 263 may include detents, fingers, levers, claws, or any other suitable device configured to grasp and releasably hold the vent assembly 233. It is noted that while the relay switches and the latching members are shown in FIGS. 2A and 2B as being separate from each other, in alternate embodiments the relay switches may be part of (e.g., substantially incorporated in) the latching members for holding the vent assembly 233 in its extended and/or retracted positions.

In operation of the vent system 230, the latching members 262, 263 may be configured so that the vent assembly 233 is released by moving the vent assembly 233 in the direction of arrow 298 (see FIG. 2A) for a short, predetermined distance for example, by a user pressing down on the duct cover 236 in the direction of arrow 298. For example, there may be sufficient clearance between the vent cover 236 and the mounting plate 280 to allow the vent assembly 233 to travel a predetermined distance in the direction of arrow 298 from its retracted position so that the latching member 263 releases the vent assembly 233 and the mechanical drive unit 270 then drives the vent assembly 233 in the direction of arrow 299 to its extended position shown in FIG. 2B. In alternate embodiments there may be a release control such as, for example, a button, switch, knob or lever that is linked to the retention unit which when activated causes the latching member 263 to release the duct assembly 233. The release control may be located in any suitable location such as, for example, on the duct cover 236 or the mounting plate 280. In other alternate embodiments the retention unit may be released in any suitable manner. The vent assembly 233 may be returned to the retracted position shown in FIG. 2A from its extended position by moving the vent assembly 233 in the direction of arrow 298 until the latching member 263 grasps the vent duct 234 of the vent assembly 233 for holding the vent assembly 233 in the retracted position. The vent assembly 233 may be manually returned to the retracted position by, for example, a user pushing the duct cover 263 in the direction of arrow 298.

Referring now to FIGS. 3A and 3B, another exemplary embodiment of a telescopic vent system 330 is shown. The vent system 330 may be substantially similar to the vent system 230 described above unless otherwise noted so that like features have like reference numbers. FIG. 3A illustrates the vent assembly 233 in the retracted position while FIG. 3B illustrates the vent assembly 233 in the extended position. As can be seen in FIGS. 3A and 3B, the vent cover 336 includes ribs but may have any other suitable aesthetic or functional features. In this exemplary embodiment a matching plate 310, which is also shown as having ribs, may be located adjacent the vent cover 336 when the vent assembly 233 is in the retracted position. The matching plate 310 and the duct cover 336 (when in the retracted position) may be configured for resting cooking utensils such as spoons, ladles and forks thereon. The matching plate 310 as well as the duct cover 336 may be removable for cleaning. In this exemplary embodiment, the mounting plate 380 includes a substantially flat surface 380F that is configured to interface with a substantially flat bottom surface 336B of the duct cover 336 for closing the vent inlet 235 when the vent assembly 233 is in its retracted position.

Another exemplary embodiment of a vent system 430 is shown in FIGS. 4A and 4B in a gas cooktop appliance, however, the system may be used in combination with electric or induction cooktop appliances as well. The vent system 430 may be substantially similar to the vent 230 described above except where otherwise noted. In this exemplary embodiment the vent assembly 433 includes a telescoping vent duct 434, a filter 431 and a vent cover 436 that all have a substantially trapezoidal cross section. It is noted that while the filter 431 is shown as being between the vent cover 436 and the vent duct 434, the filter 431 may be sized to be removably inserted into the vent cover 436 or the vent duct 434. In this example as can be seen best in FIG. 4B the vent cover 436 has vent inlets 435A, 435B located on lateral sides of the vent cover 436. Here the vent inlets 435A, 435B are located on the non-parallel lateral sides of the trapezoidal shaped duct cover 436 so that the vent inlets 465A, 465B are angled relative to each other (and relative to the rows/columns of burners 110A-110D) in a horizontal plane by any suitable angle. In alternate embodiments the vent inlets may be located on the vent duct 434 or through both of the duct cover 436 and the vent duct 434. The angled relationship between the vent inlets 435A, 435B may allow air (see FIG. 5) to be drawn from different directions from over and around the cooking area for the removal of, for example, smoke, steam and other airborne particles.

Referring to FIG. 5, the air may be drawn into the vent system 430 along two paths (e.g. one path corresponding to each vent inlet 435A, 435B) that form a substantially horizontally oriented (e.g. in a plane substantially parallel with the cooktop surface 101), substantial V-shape 500 where each leg of the substantial V-shape passes over a respective row or column of the burners 110A to 110D. In alternate embodiments, the vent inlets 435A, 435B may be located on any suitable sides of the vent cover 436 including one or more of the parallel lateral sides of the trapezoidal shaped duct cover 436. The vent inlets 435A, 435B are shown as having a rectangular shape having a height, but in alternate embodiments the vent inlets 435A, 435B may have any suitable shape and/or configuration. In other alternate embodiments the vent inlets 435A, 435B may have differing heights (e.g. the vent inlet 435A has a first height and the vent inlet 435B has a second height which is different from the first height).

Referring to FIGS. 4A and 4B, the exemplary vent assembly 433 described herein may be movable between two positions (e.g. retracted and fully extended positions). In alternate embodiments, the vent duct 434 of the vent assembly 433 may also be configured with an adjustable height so that the vent inlets can be held at any suitable height or location between the retracted and fully extended positions. In the exemplary embodiments, referring to the embodiment of FIGS. 4A and 4B as an example, the vent inlets 435A, 435B may be located at a distance B above the cooktop surface 101 when the vent assembly 433 is in the fully extended position as shown in FIG. 4A. In one example the distance B may be about seven inches, but in alternate embodiments the distance B may be more or less than seven inches. The distance B may be determined such that at most about 15% of the vented air is drawn from a bottom region GZ. Here the term bottom region GZ is used to describe the area around the burners that effects heat transfer from the burners to the cooking utensils and has a height of about 2 inches from the cooktop surface. As can be seen in FIG. 6, the higher a vent inlet is located above the cooktop surface 101, the less amount of air is drawn by the vent inlet from the bottom region GZ.

FIG. 7 illustrates a graph showing the relationship between the time it takes to boil a predetermined load (i.e. water or other liquid, such as for exemplary purposes only, a six liter load), the distance the vent inlets are located above the cooktop surface and the percentage of air captured by the vent inlets for a gas cooktop of the type illustrated in FIG. 4A. In FIG. 7, line 700 represents the time required to reach the boiling point, line 710 represents the percentage of the captured air that is drawn from the top region of the cooking area and line 720 represents the percentage of captured air that is drawn from the bottom region (e.g. grate zone) of the cooking area. As can be seen in FIG. 7, the time for the load to reach the boiling point remains substantially constant (e.g. no significant or appreciable decrease in time to boil) after the vent inlet reaches a certain distance above the cooktop. In FIG. 7, this Height Above Cooktop corresponds to the dimension B shown in FIG. 4A. For example, at a vent inlet height of about seven inches above the cooktop, less than about 10% of the vented air is drawn from the grate zone (i.e., the bottom region GZ) while more than about 70% of the vented air is drawn from a region above the grate zone.

The exemplary embodiments described herein provide a mechanically driven telescopic vent system that is integral to the cooktop and allows more heat transfer to occur between the burners and the cooking utensils. The vent system is sized such that ample room is provided on the cooktop surface to maneuver and rest cooking utensils between the burners. The mechanical drive unit may be user activated through, for example, substantial contact with the telescoping vent assembly so that inadvertent spills caused by, for example, pot handles protruding into the path of the moving vent assembly are prevented. The exemplary embodiments also allow for quieter operation and lower vent fan flow rates as well as increased burner sizes, as the size of the burners is not restricted due to the capture of air from the grate zone. In the case of gas cooktop appliances, electronic control is rarely applied due to the robustness and versatility of mechanical gas valves. This mechanical drive due to its simplicity stays true to this since there is no need for electronic controls to activate a motor or solenoid device.

Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to the exemplary embodiments thereof, it will be understood that various omissions and substitutions and changes in the form and details of devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. 

1. A vent system for a cooking appliance with a cooking area comprising a cooktop surface supporting a plurality of surface heating units, comprising: a vent box mounted substantially beneath the cooktop surface; a telescopic vent assembly telescopically mounted relative to the vent box, the telescopic vent assembly being movable between a retracted position proximate the cooktop surface and an extended position above the cooktop surface; a retention unit configured to releasably hold the telescopic vent assembly in the retracted position; and a stored energy mechanical drive unit configured to move the telescopic vent assembly in a first direction to the extended position upon release of the retention unit.
 2. The vent system of claim 1, wherein the stored energy mechanical drive unit comprises a spring system.
 3. The vent system of claim 1, wherein the stored energy mechanical drive unit is configured to move the telescopic vent assembly to the extended position within about three seconds.
 4. The vent system of claim 1, wherein the retention unit is configured to release the telescopic vent assembly when the telescopic vent assembly is moved in a second direction substantially opposite the first direction.
 5. The vent system of claim 1, further comprising a detection unit configured to detect when the telescopic vent assembly is in the extended position, wherein the vent system is operable for venting only when the telescopic vent assembly is in the extended position.
 6. The vent system of claim 1, wherein the surface heating units are arrayed in rows and wherein the telescopic vent assembly has at least one vent inlet configured to effect an airflow over and around the cooking area of the appliance when the telescopic vent assembly is in the extended position, wherein the airflow has a substantial V-shape, each leg of the substantially V-shaped airflow passing over a respective row of the surface heating units.
 7. The vent system of claim 1, wherein the telescopic vent assembly has at least one vent inlet located a predetermined distance above the cooking area of the appliance when the telescopic vent assembly is in the extended position such that at most about 15% of vented air is drawn from a relatively lower region sufficiently close to the surface heating units to effect heating performance.
 8. The vent system of claim 7, wherein the predetermined distance is about seven inches.
 9. The vent system of claim 1, wherein the telescopic vent assembly comprises a cover which is substantially flush with the cooktop surface, when the telescopic vent assembly is in the retracted position.
 10. The vent system of claim 1, wherein the surface heating units are gas burners and the appliance comprises grates positioned above the gas burners and wherein the telescopic vent assembly comprises a cover which is substantially flush with the cooktop surface or a top surface of the grates when the telescopic vent assembly is in the retracted position.
 11. The vent system of claim 1, wherein the vent box is configured for mounting to the cooktop surface such that the telescopic vent assembly protrudes through the cooktop surface when in the extended position.
 12. A cooking appliance comprising: a cooktop surface; a plurality of surface heating units located on the cooktop surface; and a vent system comprising: a vent box mounted substantially beneath the cooktop surface; a telescopic vent assembly telescopically supported by the vent box, the telescopic vent assembly being movable between a retracted position where the telescopic vent assembly is substantially disposed within the vent box and an extended position where part of the telescopic vent assembly is disposed above the cooktop surface; a retention unit configured to releasably hold the telescopic vent assembly in the retracted position; and a stored energy mechanical drive unit configured to move the telescopic vent assembly in a first direction to the extended position upon release of the retention unit.
 13. The cooking appliance of claim 12, wherein the stored energy mechanical drive unit comprises a spring system.
 14. The cooking appliance of claim 12, wherein the stored energy mechanical drive unit is configured to move the telescopic vent assembly to the extended position within about three seconds.
 15. The cooking appliance of claim 14, wherein the stored energy mechanical drive unit is configured to move the telescopic vent assembly to the extended position no faster than one second.
 16. The cooking appliance of claim 12, wherein the retention unit is configured to release the telescopic duct assembly when the telescopic duct assembly is moved a predetermined distance in a second direction substantially opposite the first direction.
 17. The cooking appliance of claim 12, wherein the telescopic vent assembly comprises a vent duct telescopically received in the vent box, the vent duct having an upper end and a vent inlet adjacent to the upper end, the vent inlet being configured to effect an airflow over and around at least one of the surface heating units when the telescopic vent assembly is in the extended position.
 18. The cooking appliance of claim 17, wherein the telescopic vent assembly further comprises a passing-through cover for covering the vent inlet.
 19. The cooking appliance of claim 17, wherein the telescopic vent assembly further comprises a filter disposed in the vent duct.
 20. The cooking appliance of claim 17, further comprising a seal disposed between the vent box and the vent duct. 